Do you need permission to sample together different songs as an intro to a mix?

Can you put different samples of songs together to make an intro as a DJ to a MIX?? for example can i put the part that that says "i can tell she wants it" from 50 cent - down and right after put the part that says "we be burnin" from sean paul followed by "drop it drop it low girl " from drop it low - lil wayne ??? just an example to get my point understood by the way lol...and use that as a intro to my mix??? Can i do that without gettin sued ?? lol or do i need permission????? not a remix to a song by the way a DJ mix...